The "experience" concept simulates that a 28 year-old player, with certain abilities, has managed to learn things not directly concerning these abilities, which thus affects his actions on the field.
Here, too, we separate two concepts.
1) Experience: An individual characteristic for each player.
2) The teams routine, with any given formation: A characteristic concerning the team as a whole.
These characteristics are applied in three different contexts during a match:
If you use a formation differing from 4-4-2, and, above all, if you choose anything other than the 6 standard alternatives (4-3-3, 5-3-2, 3-5-2, 4-5-1, 3-4-3, 5-4-1) there's an increasing risk of confusion in the team. The following decides if your team will be subject to confusion:
If the team is used to (see below) playing with a formation, the risk decreases. This is the only function of the team's routine with a certain formation.
If the players' accumulated experience (with a bonus for the team captain, see below) is high, the risk decreases.
The more the formation strays from 4-4-2, the higher the risk. 4-4-2 is completely free of risk.
A test of confusion is carried out just before the match begins. Tests can also occur during match time. If the players are confused at half-time the coach can improve the situation somewhat by giving an extra briefing.
Penalty shoot-outs: Nothing's more nerve-wracking than having to face a penalty shoot-out at the end of a cup-match or qualifier. At every penalty (not during regular match time, though) a test of the players experience is carried out. At this point, don't send forth your shaky 17-year old debutante as the first penalty taker! The skills taken into consideration include scoring ability, set piece ability, as well as the technical specialty for penalty-takers, and the keeper skill for keepers.
"Nervous situations": Very important or dramatic matches might mean that inexperienced players loose their grip on the game. This gets worse the more they lack experience. Only the team with the lowest amount of experience will be subject to this during a match. So far, this has all been about how experience and a team's routine with a certain formation is applied. How does one acquire routine and experience, then?
The players get their experience through playing league matches, national cup matches, national team matches, and friendlies (national friendlies give the players about half the experience an international friendly does).
League matches give a slightly random amount of experience, so you may see some short-term variation in how fast a player's experience increases. This variation is random and not based on the division the game is played in.
Cup matches give about double the amount of experience compared to league games.
The team's routine with a certain formation:
Every time (here, training matches are as effective as regular ones) your team plays with one of the 6 standard alternatives (4-3-3, 5-3-2, 3-5-2, 4-5-1, 3-4-3, 5-4-1), it will acquire routine with this formation. The team always has the maximum amount of experience with 4-4-2. The team can't acquire routine with formations differing from the 6 standard alternatives, so if you want to use an extreme formation, you'll have to put your trust in your players' individual experience.
If you don't play with a certain formation, routine will decrease over time. A good idea is to always use an alternative, or switch between two alternatives. If you use more, it is not surprising that the players will get confused. Also, anytime you sell a player, you will risk losing formation experience.
The Team Captain:
You can appoint a team captain for each match. When the team's total routine is calculated, all the individual players' experience levels are added. After this, a figure representing the team captain's level of experience and leadership abilities are added. This is the team captain's only function, although it's quite an important one, as he may prevent your team from getting confused due to a strange choice of formation, or getting the heebie-jeebies during cup matches or qualifiers!
The team captain has to be in the starting line up. If you haven't appointed a team captain, the players will do so by drawing lots just before the game.
Other Experience related stuff:
Experienced wingers and forwards can score using their experience.
Inexperienced defenders and inner midfielders can give their opponents an extra chance.